Polyacrylonitrile and acrylonitrile copolymers are among the polymers which exhibit rather limited miscibility with any other polymer. It is generally known that blends of styrene-acrylonitrile copolymers with polymethacrylates are miscible over a limited range of acrylonitrile content and that they exhibit phase separation on mixing or lower critical solution temperature behavior. Nevertheless, blends are known and in U.S. Pat. No. 4,452,943 a blend is disclosed comprising between 80 to 99 percent of a thermoplastic polymer and one to 20 percent of polyacrylonitrile or acrylonitrile-butadiene copolymer, having a nitrile group content of at least 14.7 percent. The invention relies on the nitrile polymers to provide polar domains that are responsive to electromagnetic radiation which, in turn, provide the uniform heating of thick thermoplastic articles manufactured from such mixtures to the proper thermoforming temperatures.
U.S. Pat. No. 4,540,754 discloses blends of acrylonitrile copolymers with 0.1 to 20 parts by weight of partially sulfonated polystyrene. Such blends are utilized to produce fibers that have good basic dyeability.
While these patents disclose blends of mixtures of polymers, one of which is an acrylonitrile polymer, the blends do not necessarily disclose high acrylonitrile containing copolymers. Such polymers are described in detail in U.S. Pat. Nos. 3,426,102, 3,586,737 and 3,763,278 owned by the assignee of record herein. They are basically thermoplastic polymer compositions containing at least 70 percent by weight of an unsaturated mononitrile, an ester of an olefinically unsaturated carboxylic acid and a rubbery copolymer of a conjugated diene and styrene or an olefinically unsaturated nitrile.
Blends of other thermoplastic polymers with these polymers are described in five U.S. patents also owned by the assignee of record herein. U.S. Pat. No. 3,914,337, for instance, discloses blends of high acrylonitrile copolymers with resinous copolymers of acrylonitrile and styrene. U.S. Pat. Nos. 4,153,648 and 4,195,135 disclose blends of high acrylonitrile copolymers with acrylonitrile-indene copolymers. U.S. Pat. No. 4,160,001 discloses blends of high acrylonitrile copolymers with a copolymer of methyl methacrylate and styrene. U.S. Pat. No. 4,307,207 discloses blends of high acrylonitrile copolymers with hydrophobic nylon.
The blends with nylon exhibit improved impact resistance and are useful in a variety of thermoformed articles. The other blends have improved gas barrier properties and other mechanical properties making them suitable as packaging materials.
Nevertheless, the present invention is directed toward additional thermoplastic polymer blends which comprise various polymers, that are widely recognized as permeable materials, in admixture with high acrylonitrile copolymers.